CN116669717A - Long-lasting in-situ forming/gelling compositions - Google Patents

Abstract

The present application provides a sustained release formulation, a method for preparing the sustained release formulation, and a method for treating localized pain in a subject in need thereof, the sustained release formulation comprising: one or more active pharmaceutical ingredients; at least one biocompatible polymer excipient; and at least one biocompatible solvent.

Description

Long-lasting in-situ forming/gelling compositions

Cross References to Related Applications

This application claims the benefit of U.S. Provisional Patent Application No. 63/066,547, filed with the U.S. Patent and Trademark Office on August 17, 2020, which is incorporated by reference in its entirety for all purposes way incorporated into this article.

technical field

The present disclosure generally relates to sustained release formulations, methods for preparing said sustained release formulations, and methods of using said sustained release formulations, wherein these sustained release formulations are in situ forming gel formulations.

Background technique

Extended-release drug delivery systems improve drug safety and efficacy by optimizing their biopharmaceutical, pharmacokinetic, and pharmacodynamic properties. Sustained-release drug delivery systems have several advantages over conventional dosage forms, such as improved patient compliance, steady-state drug levels, enhanced bioavailability, reduced side effects, lower healthcare costs. However, the development of sustained-release drug delivery systems is challenging due to the complex biological interactions and unique physicochemical properties between different drugs. Therefore, there is still an unmet need and market for long-acting products in many therapeutic areas such as pain management, antiviral, cancer therapy, CNS, etc.

The effect of local anesthetics usually lasts for several hours, which is sufficient to cover most surgical or invasive diagnostic procedures. However, after the surgical procedure, the patient still suffers from pain for a longer period of time. Prolonging the efficacy period by simply increasing the anesthetic dose may lead to severe toxic effects. Current solutions for treating this post-operative pain (POP) mainly rely on continuous administration of analgesics through different routes, such as repeated injections of short-duration local anesthetics, local anesthetic pumps, or patient-controlled analgesia (PCA). Many of these methods are inconvenient and involve the use of opioids. The use of opioids for analgesia, especially via PCA, may raise serious safety concerns, such as possible narcotic addiction, emesis, and respiratory depression. Therefore, the development of long-acting analgesic products is highly desirable for this purpose. Extended release injectable formulations have been developed to meet this need by loading one or more analgesic ingredients into the sustained release formulation carrier. The resulting co-injectable formulations enable one-time administration of POP and reduce opioid use (US 20130189349A1, US 8,834,921B2, US9,668,974, US 9,694,079, US 5,244,678).

Different approaches have been developed, such as biodegradable polymers (US 20150182512A1, US 9,694,079B2) and viscous oil formulations (US 10,206,876B2) and liposomes (US 8,834,921B2) as agents for loading analgesics and prolonging the release profile. carrier. Both opioid and non-opioid analgesics such as morphine, bupivacaine, ropivacaine and buprenorphine have been loaded into these novel sustained-release vehicles .

——The first long-acting local anesthetic product approved by the FDA in this field, since it was launched in 2012, it uses multivesicular liposomes as a delivery vehicle for loading bupivacaine to achieve a long-lasting anesthetic effect of up to 72 hours . However, the preparation of multivesicular liposome products is challenging. Drug release and duration of anesthetic efficacy of liposomal products are also limited.

US 10,213,510 describes polymer formulations developed by Heron Therapeutics, Inc. The polyorthoester material was used as a carrier for loading bupivacaine and meloxicam, a non-steroidal anti-inflammatory drug (NSAID), to achieve a long-lasting anesthetic effect of up to 72 hours. Product ZynRelief Approved for Postoperative Pain Management and Formulated as Controlled Spread Polymer for sustained delivery of bupivacaine and meloxicam. Animal and human clinical trials have shown that meloxicam is essential for prolonged efficacy, but it may increase the risk of serious cardiovascular side effects. The polymer is also used in another marketed product, SUSTOL, for the extended release of Granisetron for chemotherapy-induced nausea and vomiting. However, this formulation has high viscosity and cannot be injected without the addition of viscosity reducing ingredients.

Durect has developed the SABER long-acting platform using sucrose acetate isobutyrate (SAIB) and N-methylpyrrolidone (NMP) solvents to dissolve drug substances (US 8,153,149, Controlled Delivery System). The product will form a viscous gel matrix after injection and release the drug over an extended period of time. Due to safety and efficacy concerns, the product POSIMIR is only approved for administration in the subacromial space under direct arthroscopic visualization.

US 8,236,292B2 utilizes neutral diacyl lipids/tocopherols, phospholipids and biocompatible low-viscosity organic solvents to dissolve or disperse active pharmaceutical ingredients to prepare low-viscosity mixtures with liquid crystal phase structures. The mixture formed a viscous gel on contact with water and exhibited slow release of the drug. This fluidic crystal system can deliver both small molecules and biomolecules, such as peptides (US 8,865,021 B2, Compositions of lipids and cationic peptides). Camurus has developed many products using fluid crystal technology. PainReform Ltd. has also reported a similar long-acting technology for long-acting local anesthesia purposes (US 9,849,088, Long-acting formulations of hydrophobic active ingredients and methods for their preparation). The proliposomal oil formulation forms a liposomal structure after administration to achieve extended release of ropivacaine. Prolonged efficacy of these formulations has been reported, but the benefits are limited.

Bupivacaine hydrochloride (Xaracoll) is an FDA-approved drug/device combination product used to produce postoperative local analgesia within 24 hours of inguinal hernia repair. It uses a collagen matrix to prolong the release of bupivacaine at the surgical site (USRE 47,826 Drug Delivery Device for Providing Local Analgesia, Local Anesthesia, or Nerve Block). However, the requirements of the implant matrix at the surgical site limit the application of bupivacaine hydrochloride.

Taiwan Liposome uses multilamellar liposomes to load ropivacaine for postoperative pain management (WO 2020176568A1, pharmaceutical composition for treating pain). Clinical results suggest limited benefit compared to standard of care with bupivacaine injections.

Lipocure and VirPax prepared bupivacaine-loaded liposome hydrogels by mixing multilamellar liposomes with alginate hydrogels. The combination of multilamellar liposomes and alginate hydrogels provides delayed release of drug payloads through dual long-acting mechanisms. However, the preparation process is complex and challenging.

PLGA is a biodegradable and biocompatible material. It has been widely used in the manufacture of controlled release pharmaceutical products. Dosage forms include microspheres, in situ molding, nanoparticles, etc. Aokemesi (Alkermes) uses the oil-in-water emulsion method to load drugs such as risperidone (risperidone) and naltrexone (naltrexone) in PLGA microparticles (US 5,792,477, biodegradable biodegradable products containing bioactive agents for extended shelf life Preparation of biocompatible microparticles). After injection into the body, the drug can be released over a long period of 2 weeks to several months. Liquidia developed the PRINT technology to produce PLGA microparticles of designed shape and size that can be used to control the release of bupivacaine (US 9,744,715, Method for producing patterned materials). The Indivior company (Indivior) developed an in situ forming formulation to dissolve buprenorphine and PLGA in N-methyl-2-pyrrolidone (US 10,198,218 - Injectable flowable composition including buprenorphine). Once injected into the body, a PLGA gel matrix with buprenorphine in it forms. Buprenorphine is slowly released from the PLGA gel matrix for up to one month. However, PLGA materials will remain at the injection site for extended periods of time (2 weeks to several months), which is not ideal for applications requiring less than 1 week.

Amaca Thera Corporation (Amaca Thera) has developed a hydrogel drug delivery system using hyaluronic acid and methylcellulose. The high concentration of hyaluronic acid and methylcellulose makes the preparation and clinical practice challenging due to the high viscosity of the product.

Among various complex formulation matrix materials, hyaluronic acid is an ideal candidate material because of its excellent biocompatibility and biodegradability. Hyaluronic acid is a negatively charged polysaccharide substance naturally present in the human body and gradually degraded by hyaluronidase. Lidocaine, ropivacaine, bupivacaine and other local anesthetics have been loaded into matrices containing hyaluronic acid. To prepare a delayed-release matrix, hyaluronic acid is usually cross-linked to some extent and dissolved in water or an aqueous solution. However, hyaluronic acid formulations have the disadvantage of high viscosity, which limits the design of formulations with extended release properties. (US 10,098,961B2 Hyaluronic acid composition, KR 102030508B1 - Hyaluronic acid composition, KR20140025117A Composition of anesthetic including hyaluronic acid, WO 2019121694A1 Injectable composition of cross-linked hyaluronic acid and bupivacaine and its use , JP 4334620B2 includes a pharmaceutical product of hyaluronate with a local anesthetic.)

In addition to the advantages mentioned above, there are still limitations and unmet needs in this field. Although the first marketed complex formulation product, Exparel, claims a 72-hour duration of efficacy, there remains an unmet need for longer efficacy in the field. Polymer formulations have more potential to achieve longer efficacy, but the viscosity of polymer formulations is usually very high which makes application difficult. The use of various other materials also raises safety concerns and non-negligible side effects observed during clinical studies. Hyaluronic acid, sodium hyaluronate, and cross-linked derivatives of hyaluronic acid are highly biocompatible materials that have shown promising applications in this field, but hyaluronic acid, sodium hyaluronate, and hyaluronic acid The properties of cross-linked derivatives need to be improved by designing suitable formulations. Improved formulations with low toxicity and high biocompatibility are desired for long-lasting local anesthetic effect and ease of postoperative pain management and reduction of opioid use.

There is a need for sustained release formulations using biocompatible excipients and solvents in which the dispersed/dissolved drug content forms a partial gel with the polymer. After administration in vivo, the partially gelling polymer can be further hydrated to form an in situ gel matrix. The hydrated in situ gel matrix provides sustained release of the drug payload to surrounding tissue for long-lasting local anesthetic effect.

Description of drawings

Figure 1 represents the percentage of active pharmaceutical ingredient versus time for two novel formulations.

Figures 2A-F are photographs showing the gelation of sodium hyaluronate in dialysis bags and the release of active pharmaceutical ingredients over time in in vitro release studies. Figure 2A is a photograph after 0 minutes showing gelation and active pharmaceutical ingredient in in vitro release studies. Figure 2B is a photograph after 1 hour showing gelation and active pharmaceutical ingredient in in vitro release studies. Figure 2C is a photograph after 2 hours showing gelation and active pharmaceutical ingredient in in vitro release studies. Figure 2D is a photograph after 4 hours showing gelation and active pharmaceutical ingredient in in vitro release studies. Figure 2E is a photograph after 6 hours showing gelation and active pharmaceutical ingredient in in vitro release studies. Figure 2F is a photograph after 24 hours showing gelation and active pharmaceutical ingredient in in vitro release studies. As the in vitro release study progressed, the formulation became clearer and clear at the end of the study.

3A-F are photographs showing another perspective view of the gelation of sodium hyaluronate in a dialysis bag and the release of the active pharmaceutical ingredient over time in an in vitro release study. Figure 3A is a photograph after 0 minutes showing gelation and active pharmaceutical ingredient in in vitro release studies. Figure 3B is a photograph after 1 hour showing gelation and active pharmaceutical ingredient in in vitro release studies. Figure 3C is a photograph after 2 hours showing gelation and active pharmaceutical ingredient in in vitro release studies. Figure 3D is a photograph after 4 hours showing gelation and active pharmaceutical ingredient in in vitro release studies. Figure 3E is a photograph after 6 hours showing gelation and active pharmaceutical ingredient in in vitro release studies. Figure 3F is a photograph after 24 hours showing gelation and active pharmaceutical ingredient in in vitro release studies. As the in vitro release study progressed, the formulation became clearer and clear at the end of the study.

Figure 4 shows a graph demonstrating the in vitro release of active pharmaceutical ingredients in four disclosed formulations.

Figure 5 shows the results of a rat sciatic nerve block study of Formulations 1 and 2 versus direct administration of levobupivacaine HCl, where the graph plots response (pain) versus time. Formulations 1 and 2 showed prolonged efficacy compared to Levobupivacaine HCl samples, demonstrating the superior efficacy of the suspension formulations. Differences in drug concentration in the two formulations had no significant effect on efficacy.

Figure 6 shows the results of a rat sciatic nerve block study of Formulations 3, 4 and 5 versus direct administration of bupivacaine HCl, where the graph plots response (pain) versus time. Formulation 3 showed prolonged efficacy compared to Bupivacaine HCl. Addition of betamethasone-21-acetate in Formulations 4 and 5 further improved the duration of efficacy.

Figure 7 shows the results of a rat sciatic nerve block study of Formulations 6 and 7, where the graph plots response (pain) versus time. Both Formulations 6 and 7 showed a similar duration of efficacy. The different amounts of sodium hyaluronate used in these two formulations had no significant effect on efficacy in the rat sciatic nerve block model.

Figure 8 shows the results of an animal study of a minipig skin incision model, where the graph plots response (pain) versus time, comparing saline, levobupivacaine HCl and Formulation 8. Saline-injected minipigs felt pain 30 minutes after surgery. As the effects of isoflurane anesthesia wore off, the saline-treated minipigs showed a sharp decline in responsiveness. The efficacy of levobupivacaine HCl injection can last for about 4 hours, similar to that reported in the literature. The anesthetic efficacy of Formulation 8 lasted over 40-56 hours, which was significantly longer than that of Levobupivacaine HCl.

Contents of the invention

In one aspect, the sustained release formulations are provided herein. The sustained-release formulation comprises: A one or more active pharmaceutical ingredients; B at least one biocompatible polymer excipient; and C at least one solvent; a particle size distribution range of one of the active pharmaceutical ingredients From about 0.5 μm to about 100.0 μm. These formulations form in situ gels upon contact with water or physiological fluids.

In another aspect, provided herein is a method of preparing a sustained release formulation comprising: contacting one or more active pharmaceutical ingredients, at least one biocompatible polymeric excipient, and at least one solvent ; wherein one of the active pharmaceutical ingredients has a particle size distribution in the range of about 0.5 μm to about 100.0 μm.

In yet another aspect, provided herein is a method of treating localized pain in a subject in need thereof, the method comprising topically administering a sustained release formulation as described above.

Other features and iterations of the invention are described in more detail below.

Detailed ways

In one aspect, the present disclosure provides a sustained release formulation. The sustained release formulations provide a prolonged duration of efficacy when applied topically to a tissue area of a subject in need thereof. These sustained release formulations are useful for the treatment of localized pain in subjects in need thereof.

(I) Sustained-release formulations

The present disclosure contemplates sustained release formulations. These sustained release formulations include: A one or more active pharmaceutical ingredients; B at least one biocompatible polymer excipient; and C at least one biocompatible solvent; wherein at least one active pharmaceutical ingredient The particle size distribution ranges from about 0.5 μm to about 100.0 μm.

A One or more active pharmaceutical ingredients

The sustained release formulations encompass one or more active pharmaceutical ingredients. The particle size distribution of one of the active pharmaceutical ingredients in the sustained release formulation ranges from about 0.5 μm to about 100.0 μm.

The one or more active pharmaceutical ingredients are anesthetics, anti-inflammatory drugs (steroidal or non-steroidal), antiemetics or combinations thereof. Typically, the one or more active ingredients include bupivacaine, ropivacaine, levobupivacaine, lidocaine, buprenorphine, celecoxib, meloxicam, Dexamethasone, betamethasone, betamethasone-21-acetate, triamcinolone acetonide, nepafenac, aprepitant, cox 1 inhibitors, cox 2 inhibitors, rolapitant, fosaprepitant, granisetron, ondansetron, palonosetron, prochlorperazine ), hyaluronic acid, sodium hyaluronate, crosslinked derivatives of hyaluronic acid, or combinations thereof.

Typically, one of the active pharmaceutical ingredients has a particle size distribution in the range of about 0.5 μm to about 100.0 μm. In various embodiments, one of the active pharmaceutical ingredients has a particle size distribution in the range of about 0.5 μm to about 100.0 μm, about 5 μm to about 75 μm, about 5 μm to about 50 μm, or about 5 μm to about 15 μm, comprising All subranges in between.

Typically, the one or more active pharmaceutical ingredients range from about 0.01 wt% to about 20.0 wt% (w/w of the total sustained release formulation). In various embodiments, the weight % of the one or more active pharmaceutical ingredients based on the total weight of the formulation is in the range of 0.01 wt% to about 20.0 wt%, about 1.0 wt% to about 15.0 wt%, about 2.5 wt% to about 10.0 wt%, or 5.0 wt% to about 7.5 wt%, including all subranges therebetween.

B at least one biocompatible polymer excipient

The sustained release formulation includes at least one biocompatible polymeric excipient. Non-limiting examples of suitable biocompatible polymeric excipients may be hyaluronic acid, sodium hyaluronate, cross-linked derivatives of hyaluronic acid, PEG3350, PEG 4000, polyethylene oxide (PolyOX), Methylcellulose, hydroxypropylmethylcellulose, collagen, carboxymethylcellulose, or combinations thereof.

Typically, the at least one biocompatible polymer excipient ranges from about 0.01 wt% to about 20.0 wt% (w/w of the total sustained release formulation). In various embodiments, the at least biocompatible polymeric excipient ranges from about 0.01 wt % to about 20.0 wt %, from about 1.0 wt % to about 15.0 wt %, or from about 5.0 wt % to about 10.0 wt % , including all subranges in between.

C at least one biocompatible solvent

The sustained release formulation includes at least one biocompatible solvent. Non-limiting examples of the at least one solvent can be PEG 200, PEG 300, PEG 400, EtOH, water, polysorbate 20, polysorbate 80, propylene glycol, NMP, DMSO, benzyl alcohol, glycerin or combination.

Typically, the at least one biocompatible solvent ranges from about 5.0 wt% to about 90.0 wt% (w/w of the total sustained release formulation). In various embodiments, the at least one biocompatible solvent ranges from about 5.0 wt % to about 90.0 wt %, from about 10.0 wt % to about 75 wt %, or from about 20.0 wt % to about 50.0 wt %, comprising All subranges in between.

D Properties of Sustained Release Formulations

Sustained release formulations as detailed herein exhibit various unique properties. Sustained release formulations are in the form of suspensions, viscous mixtures or gels. Due to the particle size distribution of the one or more active pharmaceutical ingredients, the sustained release formulation suspension is part of the one or more active pharmaceutical ingredients and the at least one biocompatible polymer excipient gel. Upon contact with water or a physiological fluid such as blood, the partial gel interacts with the water or physiological fluid to form a gel. This in situ gel provides the sustained release aspect of the formulation.

The sustained release formulation provides, after administration, a duration of release of the one or more active pharmaceutical ingredients that is at least 2 times longer than that of an immediate release formulation of the one or more active pharmaceutical ingredients. In various embodiments, the sustained release formulation provides one or more active pharmaceutical ingredients for a duration of release that is at least 2 times greater than the duration of release for a direct formulation of the one or more active pharmaceutical ingredients, At least 3-fold, at least 4-fold, at least 5-fold, at least 6-fold, at least 7-fold, at least 8-fold, at least 9-fold, or at least 10-fold.

(II) Method for preparing sustained-release formulations

Another aspect of the disclosure encompasses a method for preparing the sustained release formulation. The method includes contacting one or more active pharmaceutical ingredients, at least one biocompatible polymeric excipient, and at least one solvent.

A list of suitable active pharmaceutical ingredient(s) is detailed in Section IA above. A list of at least one biocompatible polymeric excipient and at least one solvent is detailed above in Section IB and Section IC, respectively.

The components of the formulation comprising one or more active pharmaceutical ingredients, at least one biocompatible polymeric excipient, and at least one biocompatible solvent can be added stepwise in any order or in a reaction vessel or Add all at once to the reactor. In one embodiment, one of the active pharmaceutical ingredients is contacted and mixed with at least one biocompatible polymeric excipient. The combination of the one active pharmaceutical ingredient and at least one biocompatible polymeric excipient is then contacted and mixed with at least one biocompatible solvent to form a suspension, viscous mixture or gel.

One or more of the active pharmaceutical ingredients are micronized to a particle size distribution in the range of about 0.5 μm to about 100.0 μm before the process begins. Non-limiting methods for micronizing the one or more pharmaceutical ingredients can be jet milling, milling, ball milling or homogenization.

The contacting and mixing temperatures for preparing the sustained release formulations can and will depend on the particular one or more active pharmaceutical ingredients, the particular at least one biocompatible polymeric excipient, the particular at least one solvent, and the particular at least one solvent. The amount of each of these components varies. Typically, the temperature of contacting and mixing can range from 10°C to about 40°C. In various embodiments, the contacting and mixing temperature can range from 10°C to about 40°C, from about 15°C to about 35°C, or from about 20°C to about 30°C. In one embodiment, the temperature of contacting and mixing may be room temperature (about 23°C).

As will be appreciated by those skilled in the art, the duration of mixing the components of the sustained release formulation depends not only on the components, but also on when the components are sufficiently dispersed and form a suspension, viscous mixture or gel. glue. Typically, the duration of mixing can range from about 5 minutes to about one hour. In various embodiments, the duration of mixing can range from about 5 minutes to about one hour, from about 15 minutes to about 45 minutes, or from about 25 minutes to about 35 minutes.

After the sustained release formulation is formed, the formulation is stored at or below room temperature. The extended release formulation can be stored for at least 2 years.

Due to the particle size distribution of the one or more active pharmaceutical ingredients, the sustained release formulation suspension is a mixture of the one or more active pharmaceutical ingredients, the at least one biocompatible polymer excipient and the A partial gel of the at least one biocompatible solvent. Upon contact with water or physiological fluid, such as blood, the partial gel interacts with the water or physiological fluid to form an in situ gel. This in situ gel provides the sustained release aspect of the formulation.

(III) Methods of treating localized pain in a subject in need thereof

In yet another aspect, there is provided a method of treating localized pain in a subject in need thereof, the method comprising topically administering a sustained release formulation as described in section (I).

Without being bound by any theory, the formulation provides a method for treating localized pain. When administering part of the gel or suspension by subcutaneous, intramuscular, injection into soft tissue or injection into the joint cavity, these formulations are initially exposed to water or physiological fluids. On contact, these partial gels form a gel delivery matrix. The in situ gelling matrix provides delayed and sustained release of the one or more active pharmaceutical ingredients. These formulations can be used in the treatment of postoperative localized pain, nausea and vomiting (surgery, radiation, topical chemotherapy).

Suitable subjects may include, but are not limited to, humans as well as companion animals such as cats, dogs, rodents and horses; research animals such as rabbits, sheep, pigs, dogs, primates, mice, rats and other rodents Animals; agricultural animals such as cows, cattle, pigs, goats, sheep, horses, deer, chickens and other poultry; zoo animals; and primates such as chimpanzees, monkeys and gorillas. Subjects can be of any age without limitation. In preferred embodiments, the subject may be a human.

definition

When introducing elements of the embodiments described herein, the articles "a," "an," "the," and "said" are intended to mean that there is One or more of the features. The terms "comprising", "including" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

As various changes could be made in the above methods without departing from the scope of the invention, it is intended that all matter contained in the above description and the examples given below shall be interpreted in an illustrative and not in a restrictive sense.

Example 1: Preparation of samples with micronized active pharmaceutical ingredient (API) and sodium hyaluronate.

Micronized levobupivacaine was prepared using a high-speed mill. The desired API particle size was obtained by varying the mill speed. API can also be micronized using other equipment, such as jet mill, homogenizer or ball mill, etc. Depending on the formulation components, the micronized API and sodium hyaluronate were mixed well and the powder blend mixed with the PEG 300 solution to form a flowable or viscous cream suspension. In some formulations other active ingredients such as betamethasone-21-acetate are added to prolong the duration of action. The components of the formulations are listed in Table 1 below.

Table 1: Components of Formulations 1 to 8

After preparation, the formulations are subjected to assay, in vitro release testing. The anesthetic efficacy of some formulations was also evaluated in animal models.

Example 2: Preparation of formulations using micronized API and PolyOX

Different polymers can be used to prepare the formulations. Mix micronized levobupivacaine with PolyOX thoroughly. The powder blend was mixed with the PEG 300 solution to form a homogeneous suspension. The components of the 4 formulations are listed in Table 2 below.

Table 2: Components of Formulations 9 to 12

After preparation, the formulations are subjected to assay and in vitro release testing.

Table 3: Formulations 13 to 21

API-1.LBP: levobupivacaine; RP: ropivacaine.

After preparation, these formulations were subjected to assay and in vitro release testing. The efficacy of selected formulations is evaluated in animal models.

Example 4: In Vitro Release of Formulations

In vitro release of API from Formulations 6 and 7 was tested using USP Dissolution Apparatus Type 2. One gram of each formulation was carefully loaded onto a dialysis cellulose membrane column (Float-A-Lyzer G2, 1000Kd MWCO). The dialysis column was then mounted on a disso Agilent 708-DS and placed in 1000 ml of buffer (pH 6.6, phosphate-citrate buffer). During the in vitro release test, the buffer temperature was maintained at 37°C and the paddle was stirred at 100 rpm. At each desired time point, 2 ml of buffer was transferred and analyzed for levobupivacaine content by HPLC. The results are plotted in Figure 1. The in vitro release (IVR) profiles of formulations 6 and 7 were comparable despite the different levels of hyaluronate in these formulations.

Example 5: Evaluation of in situ formed hydrogels by in vitro release testing

The drug release rate is related to the formation of the hydrogel and the interaction of the drug with the hydrogel polymer. To evaluate hydrogel formation and drug release, an in vitro release study was performed to monitor the gel and drug release process. Formulation 8 was loaded into 33 x 60 mm cellulose dialysis tubing and sealed with dialysis tubing clamps. The clips are secured through holes in the floating ring. The dialysis tubing floats in the dialysate reservoir containing a stir bar and the rate of stirring is adjusted to create a gentle swirling flow. Samples were dialyzed against surfactants in phosphate buffered saline at 37°C. In-process analysis is performed by periodically withdrawing small amounts of solution from the dialysis reservoir. The dialysis tubing was also removed from the reservoir to be photographed and the total weight measured. Representative pictures of dialysis tubing are shown in Figures 2A-F and Figures 3A-F. The net weight changes are summarized in Table 4.

Table 4: Changes in net weight and different time points

time (hours) Weight (g) Net weight(g) 0 13.28 0.00 1 16.42 3.14 2 17.14 3.86 4 17.36 4.08 6 17.52 4.25 twenty four 17.55 4.27

The weight gain of the formulation in the dialysis bag during the in vitro release test is shown in Table 4, also indicative of the gelation of sodium hyaluronate over time.

The in vitro release of API from formulations 9, 10, 11 and 12 was also tested. One gram of each formulation was carefully loaded into dialysis cellulose membrane tubes (Sigma, 50k MWCO). The dialysis membrane tubing was closed with two dialysis tubing clamps and placed in 1000 ml buffer (pH 6.8, 1.0% Brij). During the in vitro release test, the buffer temperature was maintained at 37C and stirred with a magnetic stirrer at 100 rpm. At each desired time point, 1 ml of buffer was transferred and analyzed for levobupivacaine content by HPLC. The IVR results for the formulations are plotted in Figure 4. The results indicated that the addition of PolyOX slowed down the release of the drug from the formulation. The drug release rate was slower in formulations with higher molecular weight PolyOX compared to formulations with lower molecular weight PolyOX.

Example 6: Animal Study, Rat Sciatic Nerve Block Hot Plate Pain Model

A rat sciatic nerve block model was used to assess the anesthetic efficacy of the formulations. Young adult male Sprague-Dawley rats (180-220 g) were housed in groups of 4 per cage, and the rats were fed food and water ad libitum. The animal living room was controlled at 23°C with a 12 hr light/12 hr dark cycle. The needle was introduced posteromedially into the popliteal region and 0.3-1.0 mL of the test sample was injected once in contact with the bone, depositing the injection on the sciatic nerve. Test samples were injected into both hind limbs.

Thermal nociception was assessed using the hot plate test. Animals were exposed to a 50°C hot plate. The time before paw withdrawal and licking (latency) was measured with a stopwatch. If the animal did not lick its paw within 60 seconds, the experimenter removed the rat from the hot plate to prevent the development of thermal injury or hyperalgesia. All rats were tested twice on the hot plate to obtain a baseline of response prior to administration. Animals that responded too quickly (<5 s) or too slowly (>40 s) were removed. Eligible animals were then randomized into different groups with similar average response times for four animals in each group. The four groups were injected with saline, levobupivacaine HCl, formulations 1 and 2, respectively. Hot plate tests were performed at the following intervals after injection: 10 minutes, 30 minutes, 60 minutes, then hourly until no anesthetic effect or up to 18 hours. The results are presented in Figure 5 below.

Formulations 1 and 2 showed prolonged efficacy compared to Levobupivacaine HCl samples, demonstrating the superior efficacy of the suspension formulations. Differences in drug concentration in the two formulations had no significant effect on efficacy.

In another rat sciatic nerve block study, four groups of rats were injected with Bupivacaine HCl, Formulation 3, Formulation 4 and Formulation 5. The hot plate test lasts up to 24 hours. The results are presented in Figure 6 below.

Formulation 3 showed prolonged efficacy compared to Bupivacaine HCl. Addition of betamethasone-21-acetate in Formulations 4 and 5 further improved the duration of efficacy.

In another sciatic nerve block study in rats, two groups of rats were injected with Formulation 6 and Formulation 7. To minimize potential thermal damage to the rat's paw, the on-board test time was set at 50 seconds. The results are presented in Figure 7 below.

Both Formulations 6 and 7 showed a similar duration of efficacy. The different amounts of sodium hyaluronate used in these two formulations had no significant effect on efficacy in the rat sciatic nerve block model.

Example 7: Animal Research Minipig Skin Incision Model

A minipig skin incision model was used to test the anesthetic efficacy of some formulations. Minipigs are used for this model because their skin resembles that of a human.

Miniature pigs (9-12 kg) were randomly assigned to test groups. Under isoflurane anesthesia and aseptic surgical conditions, a 6 cm long incision was made in the skin on the left posterior side. Test drugs were administered subcutaneously on both sides of the incision. The wound is then closed with running sutures. After surgery, minipigs received an injection of the antibiotic amoxicillin for 3 days as wound care.

Efficacy of test drugs was assessed by Von Frey test. At desired time points, an electric automated von Frey is used to apply approximately 0.5 cm of force to the incision. If the operator observes skin/muscle contraction, or if the applied force exceeds 100 g, the operator stops the test and records the applied force reading. Test all minipigs for baseline response

And the pain threshold was set as the median value between baseline and 100g. Anesthetic efficacy is present if responsiveness is above the pain threshold, and vice versa. Anesthesia efficacy results for the minipig incision model are shown in FIG. 8 .

Saline-injected minipigs felt pain 30 minutes after surgery. As the effects of isoflurane anesthesia wore off, the saline-treated minipigs showed a sharp decline in responsiveness. The efficacy of levobupivacaine HCl injection can last for about 4 hours, similar to that reported in the literature. The anesthetic efficacy of Formulation 8 lasted over 40-56 hours, which was significantly longer than that of Levobupivacaine HCl.

Claims (20)

1. A sustained release formulation, the sustained release formulation comprising:

a. one or more active pharmaceutical ingredients;

b. at least one biocompatible polymer excipient; and

c. at least one biocompatible solvent;

wherein one of the active pharmaceutical ingredients has a particle size distribution ranging from about 0.5 μm to about 100.0 μm.

2. The sustained release formulation of claim 1, wherein the one or more pharmaceutical ingredients are anesthetics, anti-inflammatory agents, anti-emetics, or a combination thereof.

3. The sustained release formulation according to claim 1 or claim 2, wherein the one or more active pharmaceutical ingredients comprise bupivacaine (bupivacaine), ropivacaine (ropivacaine), levobupivacaine (levobupivacaine), lidocaine (lidocaine), buprenorphine (buprenorphine), celecoxib (celecoxib), meloxicam (meloxicam), dexamethasone (dexamethasone), betamethasone (betamethasone), betamethasone-21-acetate (betamethasone-21-acetate), triamcinolone acetonide (triamcinolone acetonide), nepafenac (nepafenac), aprepitant (aprepant), cox 1 inhibitors, cox 2 inhibitors, topiramate (rolipram), fosaprepinastine (fosaprepinastine), granisetron (celecoxib), ondansetron (ondansetron), betamethasone-21-acetate, betamethasone (prothionate), hyaluronic acid, or a combination thereof.

4. The sustained release formulation according to any one of claims 1 to 3, wherein the at least one biocompatible polymeric excipient comprises hyaluronic acid, sodium hyaluronate, cross-linked derivatives of hyaluronic acid, PEG 3350, PEG 4000, polyethylene oxide (PolyOX), methylcellulose, hydroxypropyl methylcellulose, collagen, carboxymethyl cellulose, or a combination thereof.

5. The sustained release formulation of any one of claims 1 to 4, wherein the at least one biocompatible solvent comprises PEG 200, PEG 300, PEG 400, etOH, water, polysorbate 20, polysorbate 80, propylene glycol, NMP, DMSO, benzyl alcohol, glycerol, or a combination thereof.

6. The sustained release formulation of any one of claims 1 to 5, wherein the sustained release formulation is a suspension, viscous mixture, or gel.

7. The sustained release formulation according to any one of claims 1 to 6, wherein the sustained release formulation is a partial gel of the one or more active pharmaceutical ingredients, the at least one biocompatible polymer excipient, and the at least one biocompatible solvent.

8. The sustained release formulation of any one of claims 1 to 7, wherein the sustained release formulation forms an in situ gel upon contact with water or a physiological fluid.

9. The sustained release formulation according to any one of claims 1 to 8 wherein the one or more active pharmaceutical ingredients range from about 0.01wt% to about 20.0wt% (w/w of the total sustained release formulation).

10. The sustained release formulation according to any one of claims 1 to 9, wherein the at least one biocompatible polymeric excipient ranges from about 0.01wt% to about 20.0wt% (w/w of the total sustained release formulation).

11. The sustained release formulation according to any one of claims 1 to 10, wherein the at least one biocompatible solvent ranges from about 5.0wt% to about 90.0wt% (w/w of the total sustained release formulation).

12. A method of preparing a sustained release formulation, the method comprising

Contacting one or more active pharmaceutical ingredients, at least one biocompatible polymeric excipient, and at least one biocompatible solvent;

wherein one of the active pharmaceutical ingredients has a particle size distribution ranging from about 0.5 μm to about 100.0 μm.

13. The method of claim 12, wherein the one or more active pharmaceutical ingredients, the at least one biocompatible polymer excipient, and the at least one solvent may be added stepwise in any order or all at once.

14. The method of claim 12 or claim 13, wherein the active pharmaceutical ingredient comprises bupivacaine, ropivacaine, levobupivacaine, lidocaine, buprenorphine, celecoxib, meloxicam, dexamethasone, betamethasone-21-acetate, triamcinolone acetonide, nepafenac, aprepitant, cox 1 inhibitor, cox 2 inhibitor, topiramate, fosaprepitant, granisetron, ondansetron, palonosetron, prochlorperazine, hyaluronic acid, sodium hyaluronate, crosslinked derivatives of hyaluronic acid, or a combination thereof.

15. The method of any one of claims 12 to 14, wherein the at least one biocompatible polymer excipient comprises hyaluronic acid, sodium hyaluronate, cross-linked derivatives of hyaluronic acid, PEG 3350, PEG 4000, polyethylene oxide (PolyOX), methylcellulose, hydroxypropyl methylcellulose, collagen, carboxymethyl cellulose, or a combination thereof.

16. The method of any one of claims 12 to 15, wherein the at least one biocompatible solvent comprises PEG 200, PEG 300, PEG 400, etOH, water, polysorbate 20, polysorbate 80, propylene glycol, NMP, DMSO, benzyl alcohol, glycerol, or a combination thereof.

17. The method of any one of claims 12 to 16, wherein the slow release formulation is a suspension, viscous mixture, or gel.

18. A method of treating localized pain in a subject in need thereof, the method comprising topically administering the sustained release formulation of claim 1.

19. The method of claim 18, wherein the subject is a human or non-human animal.

20. The method of claim 18, wherein the slow release formulation forms an in situ gel upon contact with water or physiological fluid after administration.